I first noticed the problem using two concentric curves with R2 24230 and R3 24330. The R3 was "short" compared to the R2 and on a 90 degree or 180 degree curve the end of the curved tracks would not be aligned. I looked at the elements to see if maybe the lengths were incorrect but they seemed just about right. But on the layout there clearly was an issue.
I then also noticed that using the the turnouts, 24611 or 24612, to set the 77.5mm track spacing there was something wrong there as well. Using 2 attached turnouts to set the appropriate spacing the straight tracks on either side of the turnouts were not parallel- in my case going in one direction spacing was widening the further from the turnouts the straight tracks were laid down. I only noticed this with longer straights using 6 or 7 straight tracks.
And this is what I think explains why the R2 and R3 curves do not align properly. The issue is that on a larger layouts these discrepancies compound and make it difficult to determine what track and how much of it is required when making adjustments if one strays from the perfect c track geometry- in other words you cannot tell how much is due to the software's incorrect geometry and how much is really the adjustment needed when laying down the actual track and what track lengths are effectively needed.
The problem now is also I do not wantto test all the radius geometries to see if there are issues elsewhere.
I think this is very poor for a dedicated model railroad software- particularly for a track library that is so widely used.
as already mentioned in our separate answer to your earlier email can you please provide the track plan to our support so we can have a look!
So as you can see tracks are not connected at the encircled location but shifted by a couple millimeters.
This misalignment propagates to various parts of the layout.
When reconnecting these tracks the parallel circle is also nicely aligned at the proper Märklin C parallel track distance of 77.5mm.
Same for the combination of crossing and 20224 curved track, though this is a somewhat special setup:
The way Marklin designed the C track system the 24624 double-slip turnout is a multi-purpose track that can be used in various situations.
To make all of them mostly work the track isn't a perfect replacement for the curved track but just a close match.
In general you will occasionally notice small mismatches when planning model train layouts on the computer, in particular when sectional tracks are used exclusively and no flex tracks are available.
Manufacturers primarily design track systems to make it easy to build the physical layout with a small set of tracks. These toy train tracks have reasonably large tolerances at their connection points, are always bent by small amounts and not perfectly aligned when assembled. Small errors in the manufacturers track system design usually can't be noticed there - the software however recreates the track systems in a 'perfect' world, mathematically speaking. So any error in the track system's design can show up when creating track plans in software, even though they are too small to have any effect when assembling the physical layout.
You can use the tolerance settings in the app's preferences to relax the precision requirement for connections to be recognized, or insert tiny pieces of flex track or shortened sectional tracks if desired to close tiny gaps.
It can also help to start from known configurations, e.g. start parallel track sections at their precise location and parallel track distance using the Parallel Tracks assistant and add turnouts between the track sections last instead of starting the parallel track section from a turnout or crossing (see above).
In general this is usually not an issue when planning layouts but for those curious as to why track plans don't always work perfectly in software - there you go!
Hope this helps,